In many situations, it can be desirable to image the interior of opaque objects. By way of example but not limitation, in the medical field, it can be desirable to image the interior of a patient's body so as to allow internal body structures to be viewed without physically penetrating the skin of the patient. By way of further example but not limitation, in the security field, it can be desirable to image the interior of a container and/or carrying case so as to allow the contents of the container and/or carrying case to be viewed without physically opening the container and/or carrying case.
The present invention will hereinafter be discussed in the context of medical imaging, however, it should be appreciated that the present invention is also applicable to other types of imaging, e.g., security screening, equipment analysis, etc.
Computerized Tomography (CT) has emerged as a key imaging modality in the medical field. CT imaging systems generally operate by directing X-rays into the body from a variety of positions, detecting the X-rays passing through the body, and then processing the detected X-rays so as to build a computer model of the patient's anatomy. This computer model can then be visualized so as to provide images of the patient's anatomy.
By way of example but not limitation, and looking now at FIGS. 1 and 2, there is shown a CT imaging system 5. CT imaging system 5 generally comprises a torus 10 which is supported by a base 15. Torus 10 and base 15 together comprise a frame for CT imaging system 5. A center opening 20 (which is sometimes referred to as an axial opening) is formed in torus 10. Center opening 20 receives the patient anatomy which is to be scanned.
Looking next at FIG. 3, torus 10 generally comprises an X-ray tube assembly 25, an X-ray detector assembly 30, and a rotating disk assembly 35. X-ray tube assembly 25 and X-ray detector assembly 30 are mounted to rotating disk assembly 35 in diametrically-opposing relation, such that the X-ray beam 40 (generated by X-ray tube assembly 25 and detected by X-ray detector assembly 30) is passed through the patient anatomy disposed in center opening 20. Inasmuch as X-ray tube assembly 25 and X-ray detector assembly 30 are mounted on rotating disk assembly 35 so that they are rotated as a unit concentrically about center opening 20, X-ray beam 40 will be passed through the patient's anatomy and detected along a full range of radial positions, so as to enable CT imaging system 5 to create a “slice” image of the anatomy penetrated by the X-ray beam. Furthermore, by moving the patient relative to CT imaging system 5 during scanning (or, alternatively, by moving CT imaging system 5 relative to the patient during scanning), a series of slice images can be acquired, and thereafter appropriately processed, so as to create a three-dimensional (3D) computer model of the scanned anatomy.
As noted above, X-ray tube assembly 25 and X-ray detector assembly 30 are mounted on rotating disk assembly 35 so that they are rotated as a unit concentrically about center opening 20.
In general, and looking now at FIGS. 4-9, X-ray tube assembly 25 is mounted to rotating disk assembly 35 using an X-ray tube mount 45. More particularly, X-ray tube mount 45 comprises a housing which is typically formed in two sections, an outer section 50 and an inner section 55, with X-ray tube assembly 25 being captured between outer section 50 and inner section 55. As used herein, the terms “outer” and “inner” are characterized in the context of the center of rotation of rotating disk assembly 35, i.e., inner section 55 is disposed closer to the center of rotation of rotating disk assembly 35 than outer section 50.
Outer section 50 of X-ray tube mount 45 is secured to rotating disk assembly 35, whereby to secure X-ray tube mount 45 (and hence X-ray tube assembly 25) to rotating disk assembly 35. More particularly, outer section 50 of X-ray tube mount 45 comprises two feet 60 which are secured to rotating disk assembly 35 via bolts 63 which extend through holes 65 in feet 60 and engage drum mounts 66 (e.g., brackets). Thus, holes 65 in feet 60 provide mounting constructs for mounting X-ray tube mount 45 to rotating disk assembly 35. Note that holes 65 and bolts 63 are disposed at the outer end of X-ray tube mount 45, i.e., near the outer circumference of rotating disk assembly 35. Note also that the outermost portion of outer section 50 of X-ray tube mount 45 comprises first and second lateralmost edges 67A, 67B, and that holes 65 (i.e., the mounting constructs) are disposed laterally inboard of first and second lateralmost edges 67A, 67B.
Inner section 55 of X-ray tube mount 45 includes a window 70 which emits the X-rays from X-ray tube assembly 25.
In addition to the foregoing, it should also be appreciated that X-ray tube assembly 25 generally comprises a so-called “moving anode” X-ray tube. In a moving anode X-ray tube, which is commonly used in medical scanners due to the higher energy requirements associated with medical imaging, the anode 71 (FIG. 6) of the X-ray tube assembly 25 is mounted on a shaft 72 which is rotated at a high rate of speed (e.g., up to 10,000 revolutions per minute) within the X-ray tube assembly. The cathode 73 emits electrons which are drawn to anode 71, with X-rays 40 being emitted off the anode and passing out window 70. It should be appreciated that in a moving anode X-ray tube, cathode 73 is radially displaced from the axis of rotation 74 of anode 71 (which axis of rotation 74 is sometimes referred to as “the longitudinal axis of the X-ray tube”). It should also be appreciated that in a moving anode X-ray tube, delicate bearings must be provided for shaft 72, etc., in order to sustain the high rate of rotation required for the moving anode.
It will be appreciated that any instability in the mounting of X-ray tube assembly 25 to rotating disk assembly 35 can produce variations in the X-ray beam characteristics, and hence can negatively affect the quality of the images generated by CT imaging system 5. In addition, since X-ray tube assembly 25 typically contains rapidly moving parts (e.g., an anode rotating at up to 10,000 revolutions per minute), any instability in the mounting of X-ray tube assembly 25 to rotating disk assembly 35 can cause excessive wear of the parts (e.g., bearings) within X-ray tube assembly 25, which can shorten the life of the X-ray tube assembly. It will be appreciated that, inasmuch as the X-ray tube assembly is a relatively expensive component of a CT imaging system, excessive wear of the parts (e.g., bearings) within X-ray tube assembly 25 is undesirable.
Historically, the aforementioned X-ray tube mount 45 (comprising outer section 50 and inner section 55, with outer section 50 comprising feet 60 which are secured to rotating disk assembly 35 via bolts 63 which extend through holes 65 in feet 60 and engage drum mounts 66) has performed acceptably. However, interest has now arisen in rotating the rotating disk assembly 35 with significantly increased speeds, e.g., at 270 revolutions per minute. At these increased speeds, the forces imposed on X-ray tube assembly 25 and X-ray tube mount 45 are quite large, and the conventional X-ray tube mount 45 has proven incapable of providing the requisite stability for X-ray tube assembly 25 as rotating disk assembly 35 is rotated. Among other things, instability in the mounting of X-ray tube assembly 25 to rotating disk assembly 35 has negatively affected the quality of the images generated by CT imaging system 5 and has caused excessive wear of the parts (e.g., bearings) within X-ray tube assembly 25, which shortens the life of the X-ray tube assembly.
Therefore, a new and improved X-ray tube mount is needed for mounting the X-ray tube assembly to the rotating disk assembly in a CT imaging system.